package com.yq588.forward.utils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * Utility class for working with streams.
 */
public final class StreamUtils {

	/**
	 * Private constructor, to prevent instantiation. This class has only static
	 * methods.
	 */
	private StreamUtils() {
		// Does nothing
	}

	/**
	 * Default buffer size for use in
	 * {@link #copy(InputStream, OutputStream, boolean)}.
	 */
	private static final int DEFAULT_BUFFER_SIZE = 8192;

	/**
	 * Copies the contents of the given {@link InputStream} to the given
	 * {@link OutputStream}. Shortcut for
	 * 
	 * <pre>
	 * copy(pInputStream, pOutputStream, new byte[8192]);
	 * </pre>
	 *
	 * @param inputStream
	 *            The input stream, which is being read. It is guaranteed, that
	 *            {@link InputStream#close()} is called on the stream.
	 * @param outputStream
	 *            The output stream, to which data should be written. May be null,
	 *            in which case the input streams contents are simply discarded.
	 * @param closeInputStream
	 *            True guarantees, that {@link InputStream#close()} is called on
	 *            the stream.
	 * @param closeOutputStream
	 *            True guarantees, that {@link OutputStream#close()} is called on
	 *            the stream. False indicates, that only
	 *            {@link OutputStream#flush()} should be called finally.
	 *
	 * @return Number of bytes, which have been copied.
	 * @throws IOException
	 *             An I/O error occurred.
	 */
	public static long copy(InputStream inputStream, OutputStream outputStream, boolean closeInputStream, boolean closeOutputStream)
			throws IOException {
		return copy(inputStream, outputStream, closeInputStream, closeOutputStream, new byte[DEFAULT_BUFFER_SIZE]);
	}

	/**
	 * Copies the contents of the given {@link InputStream} to the given
	 * {@link OutputStream}.
	 *
	 * @param inputStream
	 *            The input stream, which is being read. It is guaranteed, that
	 *            {@link InputStream#close()} is called on the stream.
	 * @param outputStream
	 *            The output stream, to which data should be written. May be null,
	 *            in which case the input streams contents are simply discarded.
	 * @param closeInputStream
	 *            True guarantees, that {@link InputStream#close()} is called on
	 *            the stream.
	 * @param closeOutputStream
	 *            True guarantees, that {@link OutputStream#close()} is called on
	 *            the stream. False indicates, that only
	 *            {@link OutputStream#flush()} should be called finally.
	 * @param buffer
	 *            Temporary buffer, which is to be used for copying data.
	 * @return Number of bytes, which have been copied.
	 * @throws IOException
	 *             An I/O error occurred.
	 */
	public static long copy(InputStream inputStream, OutputStream outputStream, boolean closeInputStream,
			boolean closeOutputStream, byte[] buffer) throws IOException {
		OutputStream out = outputStream;
		InputStream in = inputStream;
		try {
			long total = 0;
			for (;;) {
				int res = in.read(buffer);
				if (res == -1) {
					break;
				}
				if (res > 0) {
					total += res;
					if (out != null) {
						out.write(buffer, 0, res);
					}
				}
			}
			if (out != null) {
				out.flush();
			}
			return total;
		} finally {
			if (closeInputStream && in != null) {
				in.close();
			}
			if (closeOutputStream && out != null) {
				out.close();
			}
		}
	}

	/**
	 * This convenience method allows to read a
	 * {@link org.apache.tomcat.util.http.fileupload.FileItemStream}'s content into
	 * a string. The platform's default character encoding is used for converting
	 * bytes into characters.
	 *
	 * @param inputStream
	 *            The input stream to read.
	 * @see #asString(InputStream, String)
	 * @return The streams contents, as a string.
	 * @throws IOException
	 *             An I/O error occurred.
	 */
	public static String asString(InputStream inputStream) throws IOException {
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		copy(inputStream, baos, true, true);
		return baos.toString();
	}

	/**
	 * This convenience method allows to read a
	 * {@link org.apache.tomcat.util.http.fileupload.FileItemStream}'s content into
	 * a string, using the given character encoding.
	 *
	 * @param inputStream
	 *            The input stream to read.
	 * @param encoding
	 *            The character encoding, typically "UTF-8".
	 * @see #asString(InputStream)
	 * @return The streams contents, as a string.
	 * @throws IOException
	 *             An I/O error occurred.
	 */
	public static String asString(InputStream inputStream, String encoding) throws IOException {
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		copy(inputStream, baos, true, true);
		return baos.toString(encoding);
	}
}
